The present invention relates to a process for preparing malonate derivatives or xcex2-ketoesters by carbonylating an epoxide derivative to prepare a xcex2-hydroxyester and then oxidizing the resulting xcex2-hydroxyester. More specifically, the present invention relates to a process for preparing malonate derivatives or xcex2-ketoesters by reacting an epoxide derivative with carbon monoxide and an alcohol in the presence of a catalyst system comprising a cobalt catalyst and a promoter to produce a xcex2-hydroxyester and then oxidizing the resulting xcex2-hydroxyester.
Epoxide derivatives can be readily converted into a difunctional compound via carbonylation so that they can be used as an intermediate compound for preparing useful organic compounds. Particularly, since a 3-hydroxyester derivative has two functional groups, it has been known that it can be used as a solvent, a resin and a coating material. Further, it can be used as a raw material for pharmaceutical compounds due to its easy convertibility into other compounds, and it can also be used as an intermediate for the synthesis of alkanediols, which are the raw material for polyesters. In this regard, alkanediols are widely used as intermediates in coatings or in organic synthesis, as well as the raw materials for the synthesis of polyesters. Such 1,3-diols have generally been prepared through the hydrogenation of 3-hydroxyaldehyde derivatives which are prepared by hydroformylation of epoxide derivatives (see, e.g. U.S. Pat. Nos. 5,770,776, 5,723,389 and 5,731,478).
The present have already developed a novel process for obtaining 1,3-alkanediols in a high yield, in which an epoxide derivative is hydroesterified to synthesize a 3-hydroxyester derivative and the resulting ester intermediate is reacted with hydrogen, as well as a catalyst system useful for hydroesterification in this process, both of which are the subject of Korean Patent Application No. 2000-5357 dated Feb. 3, 2000. The present inventors have also found that malonate derivatives and xcex2-ketoesters can be synthesized in a high yield at a low cost by oxidizing or hydrolyzing xcex2-hydroxyesters under suitable conditions, and thus achieved the present invention.
Malonic acid and its derivatives, including malonate, cyanoacetate, cyanoacetic acid, malonitrile, etc., are very important compounds in the industrial field. Since such C3-dicarboxylic acid-type compounds can be used as raw materials for synthesizing derivatives such as pyrimidines, purines, etc., and further, as the starting material for numerous groups of compounds such as pharmaceuticals, flavoring agents, dyes, etc., due to their high reactivity, they have a high marketability.
Prior methods for synthesis of malonates can be summarized by the following reaction schemes. Typical examples include the hydrogen cyanide process using hydrogen cyanide and chloroacetic acid and the carbon monoxide process incorporating carbon monoxide into chloroacetate ester, as disclosed in German Patent No. 2,524,389. However, the hydrogen cyanide process has disadvantages in that it produces many other side products and also much waste water, and furthermore, noxious gases generated during the procedure are difficult to treat. Its economic practicability is lowered in all aspects, although it has some advantages in that the procedure is relatively simple and the overall yield reaches about 75-85%. Meanwhile, in the carbon monoxide process the reaction can be practiced in a good yield under mild conditions (20-80xc2x0 C., 0.12xcx9c1.0 Mpa) with a conversion rate of about 90% and a selectivity of about 95%. However, the carbon monoxide process has disadvantages in that the raw materials used in this procedure are expensive, and it also produces side products including chlorides, etc., and thus is economically undesirable (see Ullmann Encyclopedia, Vol. A16, p63).
1. The hydrogen cyanide process 
2. The carbon monoxide process (SFC) 
In the above reaction schemes, R represents CH3, C2H5 or C3H7.
In addition to the above processes, other known processes include the method of reacting ketene with carbon monoxide, the method of synthesizing malonic acid from potassium acetate and carbon monoxide in the presence of calcium carbonate and successively esterifying malonic acid, and the method of synthesizing malonic acid monoester by reacting acetate ester with carbon monoxide in the presence of alkali metal phenoxide, etc.. The method using ketene synthesizes the desired product from the very expensive and toxic starting material; and in the method starting from acetate ester, dimethylformamide used in the reaction is very toxic and difficult to remove from the resulting product, and diazomethane, which is also used together therewith, has been assumed to be a carcinogenic material and is also explosive; furthermore, the raw materials used in this method are very expensive. Alternatively, the method using carboxylation from 1,3-propanediol (see, U.S. Pat. No. 3,892,787) and the method for synthesis of malonic acid from 1,3-propanediol via oxidation (Japanese Laid-open Patent Publication No. Sho 56-5433) have also been disclosed. However, these methods are disadvantageous in that the starting material is very expensive. In addition, the method utilizing oxidation of propene with an electrochemical catalyst has been disclosed but has not been widely used industrially.
As can be clearly seen from the above, the process for preparing malonic acid derivatives or xcex2-ketoester derivatives, which comprises the steps of hydroesterifying an ethylene oxide derivative to synthesize a xcex2-hydroxyester intermediate, oxidizing the resulting ester intermediate and then adding an acid or a base or the corresponding acidic or alkaline resins thereto, has never been disclosed heretofore in the relevant technical field.
A feature of the present invention is to provide a novel process for preparing malonate derivatives or xcex2-ketoesters in a high yield, by reacting an epoxide derivative with carbon monoxide and an alcohol in the presence of a catalyst system consisting of a cobalt catalyst and a promoter to effectively produce a xcex2-hydroxyester, and then oxidizing the resulting xcex2-hydroxyester.
Another feature of the present invention is to provide a novel process for preparing malonate derivatives or xcex2-ketoesters in a high yield by developing a catalyst system comprising a cobalt catalyst and a promoter, which has a high activity and selectivity in carbonylation for converting an epoxide derivative into a xcex2-hydroxyester via reaction with carbon monoxide and an alcohol.
Still another feature of the present invention is to provide a novel process for preparing malonate derivatives or xcex2-ketoesters, in which the cost of the catalyst can be reduced by using imidazole or a derivative thereof as a promoter.
In accordance with one aspect of the present invention, there is provided a process for preparing a malonic acid monoester or xcex2-ketoester from an epoxide. The process includes the steps of (a) reacting an epoxide with carbon monoxide and an alcohol in the presence of a catalytic amount of a cobalt compound and at least one promoter to produce a xcex2-hydroxyester; (b) separating the xcex2-hydroxyester from the cobalt compound; and (c) oxidizing the xcex2-hydroxyester to produce a malonic acid monoester or xcex2-ketoester.
In specific embodiments, the promoter used in the step (a) is an imidazole derivative.
According to another particular embodiment, the epoxide is represented by the following formula (II): 
wherein R1 and R2 are independently a hydrogen atom; a C1-20 linear or branched alkyl group, a C5-10 cycloalkyl group, a C6-20 alkylcycloalkyl group, a C6-20 (cycloalkyl)alkyl group, a C7-20 aralkyl group, or a C7-20 alkaryl group, each of which can be unsubstituted or substituted with at least one F, Cl or Br; or a C6-20 aryl group which is unsubstituted or substituted with at least one F, Cl, amine group, nitrile group or alkoxy group.
In a further particular embodiment, in step (c) the xcex2-hydroxyester is oxidized in the presence of an oxidizing catalyst. According to still other particular embodiments, step (c) is carried out in the presence of a promoter. More specific embodiments recycle the oxidizing catalyst and the promoter after step (c).
According to one specific embodiment, R1 and R2 in the epoxide are hydrogen atoms, and in step (c) the xcex2-hydroxyester is oxidized to yield a malonic acid monoester. In a more particular embodiment, the malonic acid monoester is then reacted in the presence of an acid or base with an alcohol to yield a malonic acid diester. In another more particular embodiment, the malonic acid monoester is then hydrolyzed in the presence of an acid to yield malonic acid. In a further more particular embodiment, the malonic acid monoester is then hydrolyzed in the presence of a base to yield a malonic acid dianion.
In another particular embodiment, the malonic acid monoester is reacted with an alkaline base to form a salt of the malonic acid monoester.
According to another specific embodiment, R1 and R2 in the epoxide are not hydrogen atoms and R2 is not a hydroxymethyl group, and in step (c) the xcex2-hydroxyester is oxidized to yield a xcex2-ketoester.
Other feature and advantages of the present invention will become apparent to those skilled in the art from the following detailed description. It is to be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the present invention, are given by way of illustration and not limitation. Many changes and modifications within the scope of the present invention may be made without departing from the spirit thereof, and the invention includes all such modifications.